1. Field of the Invention
The present invention relates to an inkjet recording head and an inkjet recording apparatus for recording data on a material to be recorded by ejecting ink as liquid droplets. The present invention is applicable to apparatuses such as copy machines, facsimiles having a communication system, word processors having a print unit, and the like, and further to industrial recording apparatuses which are in complex combination with various processing apparatuses, in addition to ordinary printers.
In the specification, a term xe2x80x9cprintxe2x80x9d (sometimes, also referred to as xe2x80x9crecordingxe2x80x9d) not only means a case in which meaningful information of characters, graphics, and the like is formed but also widely means a case in which images, shapes, patterns, and the like are formed on a print medium or the print medium is processed so as to show them thereon regardless of that they are meaningful or meaningless and that they are made obvious so as to be visually recognized by a person or not. The term xe2x80x9cprint mediumxe2x80x9d used here not only means paper used in an ordinary printer but also widely means ink recipients such as cloth, plastic, film, metal sheet, glass, ceramics, wood, leather, and the like. Further, the term xe2x80x9cinkxe2x80x9d (sometimes, also referred to as xe2x80x9cliquidxe2x80x9d) must be widely interpreted similarly to the definition of the term xe2x80x9cprintxe2x80x9d and means a liquid which can form images, shapes, patterns, and the like by being applied onto a print medium or a liquid used to process a print medium or ink (for example, to solidify color agents in ink or to make the color agents insoluble).
2. Description of the Related Art
Recently, the performance of inkjet printers has been remarkably improved. Inkjet printers of late have realized a print speed as high as that of laser beam printers. Further, it is more and more required to increase a print speed of color images as a processing speed of personal computers is increased and the Internet becomes widespread.
A bubble jet recording system as one of inkjet recording systems is arranged such that ink is abruptly heated and vaporized by a heating element and the ink is ejected as liquid droplets from ejection ports (orifices) making use of the pressure of generated bubbles. Bubbles generated in a bubble jet recording head finally disappear because they are cooled by the ink in the vicinity of them and the vapor of the ink in the bubbles is condensed and returned to a liquid. The ink consumed by being ejected is refilled from an ink supply port through an ink supply path. Further, there is also available a recording system for abruptly heating and vaporizing ink by a heating element and ejecting generated bubbles by communicating them to the outside air.
A bubble jet recording heads according to a background art will be described. FIG. 6 is a schematic view showing a structure nozzles (ink flow paths to ejecting ports) of a first example of the bubble jet recording head according to the background art, and FIG. 7 is an enlarged schematic view showing traces of ink droplets recorded by the structure off the nozzles of the first example.
When an inkjet head as shown in FIG. 6 in which ink ejecting ports 3 and heaters (not shown), which are disposed inwardly of the ejecting port 3, are disposed in a single row, respectively, no difference is caused in the refill of ink because the ink flow paths 6 in respective segments have the same length. However, when timeshared drive is executed, positions at which ink droplets arrive are off-set in correspondence a sequence of drive, by which a problem is arisen in the formation of an imge. FIG. 7 shows a case in which linear image data is printed using even segments, wherein a straight line is printed as zigzag lines spaced apart from each other by a maximum of 42.3 xcexcm.
Whereas, when the timeshared drive is not executed, a problem is arisen in that a value of a current which instantly flows to heaters and electrodes increases and a voltage is dropped, and thus a print fades when an image of high duty is printed.
Another background art of a bubble jet recording head will be described. FIG. 8 is a schematic view showing a nozzle structure as a second example of the bubble jet recording head according to the background art.
In FIG. 8, the nozzles have a density is 600 dpi. A heating element (not shown) and an ink ejecting port 3 are disposed in a nozzle at positions which are different on a segment 0 side (even segments) and on a segment 2 side (odd segments). That is, the ink flow paths 6 on the even number segment side are made longer in a sequence of the segment numbers 2, 4, 6, 8, and 0, whereas the ink flow paths 6 on the odd number segment side are made shorter in a sequence of the segment numbers 3, 5, 7, 9, and 1, whereby the above problem of the first example is solved. In FIG. 8, an ink supply path 1 is disposed vertically at a center, and ink is supplied to the respective nozzles from a segment 0 to a segment 255 through the ink flow paths 6 having a different length.
Since a lot of nozzles, that is, 256 nozzles are provided, a value of a current which flows instantly is suppressed by executing a timeshared drive as described below. In the even segments, the eight nozzles of the segments 0, 32, 64, 96, 128, . . . , 224 are arranged as a first block, and the eight nozzles of the segments 10, 42, 74, . . . , 234 are arranged as a second block. Whereas, in the odd segments, the eight nozzles of the segments 17, 49, 81, 113, . . . , 241 are arranged as a first block, and the eight nozzles of the segments 27, 59, 91 . . . , 251 are arranged as a second block. In this construction, respective eight nozzles of the odd and even side segments are arranged as one block unit, and the odd side segments and the even side segments are divided into 16 blocks, respectively. Since the arrangements of a third block to a sixteenth block are similar to those described later, the description of them is omitted here.
When the image data of the segments 0 to 31 shown in FIG. 8 is turned ON and flows, drive pulses are applied to the heating elements of the segments 0 to 31 in a sequence of the block numbers 1 to 16. At that time, the drive pulses are applied to the respective blocks at intervals of 5.9 xcexcs and drive every 16 nozzles on one side. In the even segments, a segment having a larger distance (hereinafter, referred to as C-H distance) between an heating element and an ink supply port (a position 5 branched from an ink supply path) is driven earlier. Whereas, in the odd segments, a segment having a shorter C-H distance is driven earlier.
When the drive pulses are applied to the heating elements, ink droplets are ejected from ejecting ports. While consumed ink is refilled from the ink supply ports through the ink supply path 1, a time at which the ink is refilled to a segment having a longer C-H distance is delayed as compared with a time at which it is refilled to a segment having a shorter C-H distance by the difference of the distance thereof. Thus, a problem is arisen in that the throughput of a printer cannot be increased because a response cycle must be set in accordance with a long C-H distance to obtain good print quality.
In contrast, while a fixed C-H distance can be set to all the nozzles when the ink supply ports are disposed zigzag, a problem is arisen in this case in that a refill time is delayed because the width of the supply ports of the portions thereof disposed zigzag is narrowed.
Accordingly, it is an object of the present invention to provide an inkjet recording head and an inkjet recording apparatus capable of maximizing a refill cycle while keeping the linearity of an image even if timeshared drive is executed and capable of improving the throughput of a printer.
Another object of the present invention is to provide an inkjet recording head and an inkjet recording apparatus for ejecting ink droplets in an off-set state without changing a length of ink flow paths to keep the linearity of an image.
A still another object of the present invention is to provide an inkjet recording head having a plurality of ink ejecting ports and a plurality of energy generating elements respectively positioned in confrontation with the ink ejecting ports for generating energy utilized to eject ink from the ink ejecting ports, the plurality of ink ejecting ports and the plurality of energy generating elements being divided into a plurality of blocks, and the ejecting ports and the energy generating elements being timeshared driven in a sequence of the blocks in a common driving period, wherein the plurality of energy generating elements are disposed in an approximate straight line, and the respective ink ejecting ports are off-set with respect to the energy generating elements in a projecting relationship in correspondence to the sequence of the timeshared drive and to provide an inkjet recording apparatus having the inkjet recording head.
A further object of the present invention is to provide an inkjet recording head having a plurality of ink ejecting ports and a plurality of energy generating elements respectively positioned in confrontation with the ink ejecting ports for generating energy utilized to eject ink from the ink ejecting ports, the plurality of ink ejecting ports and the plurality of energy generating elements being divided into a plurality of blocks, and the ejecting ports and the energy generating elements being timeshared driven in a sequence of the blocks in a common driving period, wherein the plurality of ink ejecting ports are disposed in an approximate straight line, and the respective energy generating elements are off-set with respect to the ink ejecting ports in a projecting relationship in correspondence to the sequence of the timeshared drive and to provide an inkjet recording apparatus having the inkjet recording head.
According to the present invention, since any ones of the energy generating elements and the ink ejecting ports are disposed in the approximate straight line and the positions of the energy generating elements are relatively off-set with respect to the positions of the ink ejecting ports, the linearity of an image can be maintained even if the timeshared drive is executed. Further, when the intervals between the energy generating elements and the positions where ink flow paths are branched from ink supply ports is made as short as possible within a range of allowance required in manufacture as to all the nozzles, a refill cycle can be maximized, whereby a throughput of a printer can be improved.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.